Grid controlled electron tubes



canin-* 1 Allg. 27, 1957 T. w. SMALL 2,804,566

GRID CONTROLLED ELECTRON TUBES Filed Dec. 2, 195s 2 sheets-sheet 1 J1 INVENTOR. THEoQA MSM/ML www HTTOE'NEY Aug. 27, 1957 T. w. SMALL 2,804,565

GRID CONTROLLED ELECTRON TUBES Filed Dec. 2, 1953 2 Sheets-Sheet 2 TETE' 58 IN V EN TOR. Esopo/e5 W- SMALL BY l 4 TOR/v r @nm cortrnorrnn arnc'rnoN TUBES Theodore White Small, Phoenixville, Pa., assignorto Philco Corporation, Philadelphia, la., a corporation of Pennsylvania Application YDeeernher 2, 1953, Serial No. 395,771

11 Claims. (Cl. S13- 248) This invention relates to electron tubes and more especially to tubes having one or more grid electrodes.

A principal object of the invention is to provide an improved grid electrode structure for electron tubes.

Another object is to provide a novel grid electrode structure and lead-in which is particularly advantageous in tubes for use in high frequency circuits.

A further object relates to improvements in grid controlled tubes for use in grounded grid amplifiers, oscillators, and the like.

A feature of the invention relates to an electron tube having a wire wound grid of highly rugged construction and wherein the grid laterals can be made parallel to each other to form a so-called flat grid, without requiring special presetting of the grid turns.

Another feature relates to a wire wound grid electrode wherein the line wires or turns of the grid are supported on a double-windowed cylindrical frame whereby the finished grid is extremely rigid. f

Another feature relates to a unitary grid frame and lead-in element whereby the grid lead-in inductance is reduced as compared with the conventional lead-in construction, and the finished grid unit is of highly rugged character.

A further feature relates to a grid-controlled electron tube wherein the undesirable characteristics of the conventional grid side rods are reduced to a minimum.

A further features relates to a novel grid electrode structure for electron tubes whereby greater mutual conductance can be obtained.

A further feature relates to a novel glass stem and sealed in grid frame unit of cylindrical contour which enables the grid frame itself to be used as a rigid winding mandrel for the tine wire wound grid laterals.

A still further feature relates to the novel organization, arrangement, and relative location and interconnection of parts which cooperate to provide an improved rugged high frequency electron tube.

Other features and advantages not particularly enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing which illustrates the invention in certain of its preferred forms.

Fig. l is a perspective View of an electron tube embodying the invention.

Fig. 2 is a sectional view of Fig. 1, taken along the line 2 2 thereof.

Fig. 3 is a sectional view of Fig. 1, taken along the line 3 3 thereof.

Fig. 4 is a sectional view of Fig. 3, line 4 4 thereof.

Fig. 5 is a sectional view of Fig. 3, line 5 5 thereof.

Fig. 6 is an exploded view of the novel electrode spacers according to the invention to explain their manner of assembly in the electrode mount.

Fig. 7 is a perspective View of the grid frame and grid lead-in element according to the invention.

taken along the taken along the aint i u It Fig. 8 is a schematic plan view of a conventional tube of the elliptical grid kind, referred to in explaining certain advantages of the invention.

Fig. 9 is a view of a modified elliptical grid tube ernploying certain features of the invention.

Fig. l() is a schematic plan view of a conventional tube of the circular grid type referred to in explaining certain advantages of the invention.

Fig. 11 is a schematic plan view of a circular grid tube embodying certain features of the invention.

Fig. 12 is a schematic plan view of a conventional flat grid, flat cathode tube referred to in explaining certain features of the invention.

Fig. 13 is a schematic plan view of a flat cathode, at grid tube embodying features of the invention.

Fig. 14 is a schematic plan view of a modification of the invention.

Referring to Figs. 1-6, the numeral 10 represents a header of glass, ceramic or other similar insulating material through which the lead-in members for the various electrodes and elements of the tube mount, are sealed in a vacuum-tight manner. The header 10 serves as the base or support for the various elements of the mount which, for simplicity in the drawing, is shown as of the triode ldnd having a central electron-emitting cathode 11 which may be a cylindrical or rectangular shaped cathode sleeve with its usual internal insulated heater element (not shown), a grid electrode 12, and a plate or anode electrode comprising for example oppositely arranged rectangular channel shaped metal sheets 13, 14, electrically connected by ametal strap (not shown) to join them electrically. The electrode mount is enclosed by a suitable bulb 15 which is sealed in a vacuum-tight manner to the rim or edge of the header 10.

ln accordance with one feature of the invention, the mount is assembled to form a rugged unit and is supported on the grid lead-in member 16 which is in the form of a cylindrical metal tube sealed centrally through the glass header l0 by any well-known sealing technique, so as to have portions projecting exteriorly and interiorly of the tube. Member 16 extends upwardly interiorly of bulb 15 and the walls of this upwardly extending portion are cut out to provide substantially semicylindrical opposite windows 17, 18, while leaving the uncut portions 19, 20, to form rigid diametrically opposite metal uprights around which the ne wire 21 can be wound, for example as a plural-turn helix. Thus, the wire 21 forms a wire wound grid wherein the grid laterals on one side of the cathode 11'are in the same flat plane and the grid laterals on the opposite side of the cathode are also in a flat plane, both planes being parallel to each.

other.

The spacing of these grid laterals from the cathode is determined by the width of the portions 19, 20 of the grid lead-in and support member 16, and the desired flatness and parallelism of the two sides of the grid can be achieved without subjecting the grid wires to a special flattening operation which may be necessary when conventional grid side rod supports of round cross section are employed, and as will be explained hereinbelow in connection with Figs. 8 through 13.

Thus, the members 19, Ztl, not only serve as the usual rigid side supports for the fine wire wound grid but they also predetermine the spacing of the opposed grid laterals. lt is highly important to certain types of tubes to have the grid as close as possible to the cathode but without danger of the grid laterals touching the cathode. The structure shown in Figs. 1 to 6, enables this result to be obtained by a simple winding operation of the line grid wire around the novel grid frame support, and the width of the portions 19, 20, can be made any desired size to determine the spacing of the grid laterals with respect 3 to the cathode. I have foundv that with this method of winding and supporting' the grid wire it is not necessary to subject it to exceptional tensioning during the winding operation as would bethe .case with: conventional round grid side r'od supports.

In accordance with another feature of theinvention and as ay resultv of the construction of memberV 16, I have found that extremely finefwire can .be `used for the. grid turns andA it-is possible to hold. the adjacent turns in their original wound spacing by. subjecting the. member -16 where the grid turns are wound thereon to a silver platingoperation. This silver plating provides sucient anchorage of .the iinewire to the members 19 and 20, andavoids the conventional and. costly operations of welding or peening thefinewire gridturnsfto their respective side rods. However, prior. to-plating the turns in place onmembers 19-and 20, the extreme ends ofthe wound wire canbe anchoredtothe members 19 and 20 by a suitable cementsuch for example as` amyl acetate or polystyrene.

For, the purpose of holdingv the cathode and plate electrodes. in proper-spaced relationto the grid, a. conventionaltop. mica disc. 22may be. used, havingl a central opening to receive the upper end23 of the cathode.

When the cathode sleeve 11 is rectangularin 'cross-section as. illustrated in the drawing, the mica disc 22 has a corresponding centrally locatedfrectangular opening through which closely lits the projecting end of the cathode sleeve. Of course, if the cathode sleeve 11 is circular in crosssection, the central opening in the mica disc 22 would be circular in shape. Likewise, the upper edge of grid member 16 has a pair of integralv lugs 24, 2.5, which project throughy corresponding openings in the top mica' 22. Similarly, the upper edges ofthe plates 13 and 14 have integral lugs 26, 27, 2S, 2,9, which project through corresponding openings in the mica 22 and these lugs are bent back to anchor the said plates against the mica, 22. For the purposeof anchoring the lower end ofthe cathode and plate elements there- ,are provided two substantially T-shaped mica members V30, 31, each havinga. central narrowing 32, 33, and a cross lug-34,35. The mica is assembled with the leg portion 32 extending through the windowed portions 17 and 18 ofthe grid lead-in and vgrid frame unit 16. The leg portion 32 has a pair ofl slots 36, 37, which are-adapted to fit overand receive integral lugs 38, 39, on the grid frame. In the case of a rectangular cathode sleeve, the leg 32 also has a rectangular slot to receive the lower end 41 of the cathode. The mica spacer 31 is then assembled in place with its leg 33 overlying the leg 32 of member 30. Theleg 33 has slots 41, 42, similar toslots 36 and 37 to receive. the lugs 38 and 39. L eg 33 also has a roundopening 43 through which passes the lower end of cathode 11. However, the diameter-of hole t3-should be greater than the maximum dimension of hole 40. In other words the cathode sleeve is supported only by the lower. mica 30, andit passes freely through thehole 43'in mica. 31. If the cathode sleeve 11 is circular in crosshsectiomthen the cathode holes in all the micas 22, 30 and 31, will be circular in shape to t the cathode sleeve. Preferably, the cylindrical lower portion of member 16 is undercut as indicated by the numerals 38A, 38B, so as to.provide clear spaces orwindows beneath the. mica 31 and through which may freely pass thev cathode connection tab 11n and the cathode heater wire ends 11b. When the two mica members 30 and 31 have thus been assembled the lugs 38 and 39 are bent outwardly to. anchor the said micas in place. The mica members 30, 31, also have openings 44, 45, 46, 47, to receive corresponding integral lugs on the lower edges of plates 13 and, 14 and these lugs can be bent outwardly to anchor thesaid plates to the micas 31) and 31.

After the mount has been assembled the connections between the cathode heater element (not shown) and its lead-in members, for example lead-in membersAS,

4 49, can be made. Likewise, a suitable connection between the plates 13, 14, andthe respective lead-in member, for example member 50, may also be made. The lead-in for the grid electrode is of course provided by the externally projecting portion of the member 16. The member 16, because of its large diameter, provides a more ecient coupling to a high frequency circuit. For example, it can be telescoped in spaced relation over the tubular. conductor 51 whereby the grid can be capacitivelyk coupled into a suitable circuit. This large diamcter lead-in for the grid also reduces the effective selfinductance of the said lead-in, as compared with the convcntional lead-in wire or prong.

The manner of assembling of the various elements of the mount will be clear from the foregoing. However, one of the important novel features of the invention is that the grid element 16 when sealed into the glass header 10 Vcan be used directly as a Winding mandrel for the tine wire grid 21. Thus, the header 10 with the sealedin member 16, can be fastened in a suitable rotating chuckand the wire 21 can be wound around the members. 19 and-20 by using the member 16 itself' as the wvindingmandrel. This is possible because the elements 19 and 20 form. a highly rigid unit with the cylindrical or non-windowed portions of member 16. Heretofore, in winding conventional grids employing conventional side rods the said side rods must be assembled in a suitable arhorwhich must be accurately machined and designed to enablethe wound grid to be removed therefrom after the winding is completed. All that is necessary: accordingto the present invention, is to support the header 10 with its sealed-in element 16 in a rotatable chuck. Oneend of the tine wire 21 can then be cemented., for example to the outer face of. member.v 19` adjacent one end. thereof and the said wire 21 can then be given the desired lead as-it is being wound. When the desired. number .of turns have been wound, the. last turn .canbexcementedto .the appropriate member 19. or 20, and then severed. The unit consisting of .elements 10,.16and 21, can. then be removed from the winding chuck and the turns of the winding 21 can be vpermanenty fastened in .place by subjecting the members 18 and 19.andthe Wire 21where it contacts thes'aidmembers 19 and 20 to a suitable plating operation, such for example as silver plating.

Afterthe grid turns have thus been anchored )in place on members 19 and 20, the mica element 30. is assembled as above described whereupon the lugs 38 and 39 are bent outwardly. The cathode 11 can then `be inserted withits lower. flattened end projecting through the mica 30 and this projecting end can, be. provided- With.the usual .connection tab 11a. The plate elements 13 and 14 can. thenbe assembled in place and the lugs on their lowery edgesbentback to anchor them to the micas 30 and 31. VThe top mica 22 may then bev assembledin placeand the corresponding lugsv24, 25, and 26-29, bent to anchor the top mica in place.

Apart vfrom the fact that thestructure as hereinabove described provides a highly rugged tube mount, is the fact that the grid construction as. described produces electrical characteristics which are also of great importance, particularly in high frequency and ultra high frequency` circuits. The invention 'enables the tube'to be used with a grounded grid in ultra high frequency circuits while obtaining. llow lead-ininductance.

Furthermore, the unit consisting of the 'header 10 and theelements 16 and 21 is in itself extremely rugged because of the strength of the cylindrical tubing fromvwhich theelement 16.is.made. This unitcanthen .be handled in large quantities without too much danger of the grid turns being distorted with respect to the rest ofthe grid. Furthermore, it is possible to handle the unit without touching the grid turns themselves since'the unit can be handled byifmeans of the glass header 10, thus reducing the chance of contaminatinggcontactwith,the.gridaturns Furthermore, because of the particular structure, when the unit consisting of elements-10, 16 and 21 is placed in a tray or other carrier, the wound length of the grid 21 always remains out of contact with the surface of the carrier, thus further reducing the likelihood of deformation, or contact contamination of the grid turns.

It will be understood, of course, that the invention is not necessarily limited to a grid of the wire wound type. For example, as shown in Fig. 14, the grid frame 16 can have sheets of fine wire mesh attached to the edges of the members 19 and 20 and fastened thereto by plating.

While Figs. 1 through 7, and Fig. 14, relate to a tube of the so-called flat grid type, the invention has advantages in tubes wherein the grids are elliptical, circular or other shape. In Fig. 8 there is shown in schematic plan View, the cathode and grid and anode of a typical conventional tube wherein the central cathode 54 is surrounded by elliptical wound grid 55 which is welded or otherwise attached to the conventional round grid side rods 56, 57. This grid is then surrounded by a tubular plate or anode 5S. The side rods 56 and 57 have substantial thickness considered radially with respect to the cathode 54 so that when they are negatively polarized they cast both a physical and an electric shadow on the plate 5S as represented by the shaded portions 59 and 60. On the other hand, and as shown in Fig. 9, by using a grid frame and lead-in construction, such as illustrated in Fig. 7, the members 19, 2t), have very little thickness considered radially of the cathode 54. Furthermore, for a given mechanical strength, it is possible to make the Width of the members 19 and 20 relatively small so that the physical and electron shadow on the anode S8 can be made much smaller.

Furthermore, in certain types of tube construction it is possible, because of the reduced radial thickness of the members and 2t?, as compared with the conventional round side rods, to bring the grid turns closer to the cathode without corresponding liability of shortcircuiting between the cathode and grid. For example, as shown in Fig. l0, with the conventional round side rod construction, the minimum spacing between the grid turns and the cathode is limited by the radial thickness of the grid side rods, whereas in the embodiment of Fig. ll using a grid frame such as element 16 the relatively small radial thickness of the members )i9 and 20 enables the grid wire to be brought substantially closer to the cathode.

A further advantage of the invention as applied to flat type grids is that it avoids the step of forming or setting the grid laterals in order to achieve the necessary parallelism between a liat type cathode. Thus, there is shown in Fig. l2, a conventional tube structure employing a liat cathode 61 which is surrounded by a ne Wire grid 60, this grid being attached to and supported on conventional round side rods 63, 64. Because of the springiness of the usual grid wire 62, it has been found that in certain types of tubes it is necessary to deform or bend the wires inwardly, as indicated at 65, in order to preserve the necessary parallelism between the remaining length 66 and the hat faces of the cathode 61. This grid-forming operation has been found to be comparatively expensive and diiicult of control. As shown in Fig. 13, by employing a grid frame such as the element 16 with the integral support members i9 an'd 2t), the winding of the line grid Wire 21 therearound automatically maintains the desired parallelism with the at type cathode 61.

While the invention is not limited to any particular materials, it will be understood that the member 16, or at least that portion of it which is in Contact with the glass header 10, is of a metal or alloy having substantially the same expansion coeicient as the glass of the header.

Various changes and modications may be made in the disclosed embodiments without departing from the spirit and scope of the invention.

What is claimed is:

l. An electron tube mount comprising a tubular metal grid frame having a pair of oppositely disposed cutout Windows defining a pair of oppositely disposed integral ribs, a pair of insulator spacer members each inserted respectively through said windows, said spacer members extending internally across the tubular member and anchored thereto, each of said insulator spacer members when superposed having aligned openings located at the center of sai-d tubular member to receive one end of a cathode electrode.

2. An electron tube mount according to claim l, in which the lower edge of each of said windows has an integral tab, and each of said spacer members has a pair of openings in interlocked engagement with said tabs.

3. A grid electrode for electron tubes comprising a tubular metal member having oppositely disposed cutout windows defining a pair of remaining integral ribs, and a foraminous grid element extending transversely between said ribs and anchored thereto and forming with said ribs a tubular discharge chamber whose outer boundary is Well within the outer boundary of said tubular metal member.

4. A grid electrode according to claim 3, in which metal plating means anchors said foraminous grid element to said ribs.

5. A grid electrode for electron tubes comprising a tubular metal member having oppositely disposed cutouts defining a pair of windows with the remaining uncut part defining a pair of integral oppositely disposed ribs, each of said ribs having a width which is only a small fraction of the peripheral dimension of said member, and a grid wire wound around said ribs and extending transversely to the rib length and having the turns thereof anchored to said ribs and forming with said ribs a tubular discharge chamber whose outer boundary is well within the outer boundary of said tubular metal member.

6. An electron tube, comprising an enclosing envelope, a unitary tubular metal member sealed vacuum-tight through the wall of the envelope and having one portion projecting externally thereof to constitute a lead-in member, and another portion extending internally of the envelope to constitute a rigid electrode mount support, said mount including a cathode, a grid, and an anode, and insulator spacer means insulatingly spacing the cathode, grid and anode from each other, and means comprising the said internally projecting portion of said tubular member for supporting said cathode, grid and anode therefrom as a unit.

7. An electron discharge tube comprising, an enclosing envelope, said envelope enclosing a plurality of cooperating electrodes one of which defines a tubular discharge chamber; said chamber comprising a tubular metal member sealed vacuum-tight through a wall of said envelope and having a portion extending interiorly of the envelope and a portion extending exteriorly of the envelope, said interiorly extending portion having oppositely disposed windows defined by a pair of oppositely disposed ribs forming an integral part of said tubular member and foraminous conductive means extending across each window and fastened to said ribs, said foraminous means being located within the boundary defined by the periphery of said tubular member.

8. An electric discharge device according to claim 7, in which said tubular member is cylindrical and said foraminous means is in the form of a fine wire wound around said ribs so as to form said oppositely disposed walls which are substantially planar and parallel.

9. An electric discharge device according to claim 7, in Which said tubular member is cylindrical and said foraminous means is in the form of a fine wire wound around, said` ribsA so as to formsaid oppositely disposed walls which are arcuate; t

10. An electron tube mount unit accordingfto clairrnlT, in which a pair of insulator spacer members.. are provided each having; a portion inserted throughsaidwindovvs, and anchored to` said, tubular member, each: of, said; spacer members also` having a portion extendingv radially` outward from said tubular member, and atleast one other electrode anchored to said insulatormembers.

11. An electron tube mount unit accordinggto claim; 7, in which an electron-emitting cathode isl located centrally within said tubular metal member andan anode electrode is arranged in spaced relation to the. outside of said cylindrical metal member, and means interlocking said tubular member, said cathode vand said'. anode as a, unit and includingv a pair ofinsulator. spacer members` each having a portion inserted through said windows and inter- 8. locked-with said tubular metal memben, each of'-said;insulator; spacer members. having-aligned openings located inside said Ytubular lmember receiving-and anchoring one` end of saidcathode,; eachof said insulator spacer rmembers having'a portion extending, radially away from said tubular metal member and having meansy interlocking said spacerv membersV with said anode electrode.

References Cited in the le of this patent UNITED STATES PATENTS AL,... Ew 

